As a gas sensor provided with a heating element, there is, for example, a thermal gas sensor that measures a gas amount from a radiation amount of the heating element exposed in the gas by using a change in heat conductivity of the gas. The thermal gas sensor is used in various technical fields, and, in an internal combustion engine for vehicles, is required for measuring environmental conditions such as humidity in addition to the flow rate of the intake air, temperature, and pressure, with high accuracy in order to realize lower power consumption. In addition, in the internal combustion engine for vehicles which use hydrogen as fuel, the sensor is used for optimally operating the internal combustion engine by detecting the concentration of hydrogen.
As the thermal gas sensor that measures humidity or the concentration of gas such as hydrogen, there is a gas sensor disclosed in PTL 1. The gas sensor includes a substrate with a cavity portion; a thin-film support that is stacked in the cavity portion and is configured of a plurality of insulating layers; and a first heating element and a second heating element which are interposed between the insulating layers in the thin-film support, in which the second heating element is disposed around the periphery of the first heating element, the first heating element is controlled to have a higher temperature than that of the second heating element, and a concentration of an ambient gas is measured based on electric power applied to the first heating element.
In addition, as the gas sensor provided with the heating element, there is an exhaust gas sensor provided with a heater for heating a detection element disclosed in PTL 2.